Maturation and Reproduction in Two Hawaiian Eteline 

 Snappers, Uku, Aprion virescenSy and Onaga, Etelis 



coruscans 



Alan R. Everson, Happy A. Williams, and Bernard M. Ito 



ABSTRACT: Size at sexual maturity, spawning 

 season, and pattern of egg release were determined 

 for two of Hawaii's commercially important snapper 

 species: uku, Aprion virescens, and onaga, Etelis 

 coruscans. Sexual maturity of females was assessed 

 by macroscopic and microscopic (oocyte measure- 

 ment and histology) techniques and gonosomatic 

 indexes. Interspecific differences were noted in 

 many aspects of the reproductive biology. Both 

 species had protracted spawning seasons: uku 

 spawned in May-October while onaga spawned in 

 June-November. Female size at sexual maturity 

 was 425-475 mm fork length (FL) for uku and 675- 

 725 mm FL for onaga. Both species were deter- 

 mined to be multiple spawners, although the num- 

 ber of batches spawned per season could not be 

 established. 



Uku, Aprion virescens, and onaga, Etelis cor- 

 uscans (Lutjanidae), are species of considerable 

 importance in terms of total landings and value 

 to bottom fish fisheries in southern Japan 

 (Masuda et al. 1975), Guam, the Northern Mar- 

 ianas (Amesbury and Myers 1982), Vanuatu 

 (Brouard and Grandperrin 1985), American 

 Samoa (Western Pacific Regional Fishery Man- 

 agement Council (Council) 1986), and Hawaii 

 (Ralston and Kawamoto'). In addition, many 

 other Pacific island nations have subsistence and 

 commercial fisheries for these species. In 

 Hawaii, uku and onaga ranked second and third, 

 after Pristipomoides filanientosus, in total catch 

 and value among bottom fish species in 1984 

 (Pooley 1987). 



Both species are widely distributed through- 

 out the tropical Indo-Pacific. Uku range from 



'Ralston. S.. and K. E. Kawamoto. 1987. An assess- 

 ment and description of the status of bottom fish stocks in 

 Hawaii. Southwest Fish. Cent. Honolulu Lab., Natl. Mar. 

 Fish. Serv.. NOAA, Honolulu. HI 96822-2396. Southwest 

 Fish. Cent. Admin. Rep. H-87-7, 55 p. 



Alan R. Everson, Happy A. Williams, and Bernard M. Ito, 



Southwest Fisheries Center Honolulu Laboratory. National 

 Marine Fisheries Service, NOAA, 2570 Dole Street, Hono- 

 lulu, HI 96822-2396. 



East Africa to Hawaii and from southern Japan 

 to Australia (Allen 1985), and onaga e.xtend to 

 the Atlantic coasts of South America and Africa 

 (Druzhinin 1970). Uku are caught at the surface 

 by trolling gear and at < 300 m depths by deep- 

 sea handline gear (Druzhinin 1970), whereas 

 onaga are restricted to deeper waters between 

 220 and 320 m. In Hawaii, the gi'eatest portion of 

 the uku and onaga catches comes from the Pen- 

 guin Bank region, which is southwest of Molokai 

 in the main Hawaiian Islands (Ralston^). 



Relatively few reproductive studies have been 

 completed for the commercially important bot- 

 tom fishes of the western Pacific, even though 

 such information represents a critical component 

 of the biological basis of management for the 

 bottom fish and seamount gi'oundfish fisheries in 

 this region (Council 1986). Some information is 

 available on Hawaiian stocks oi P. filamentosus 

 (Ralston 1981; Kikkawa 1984), Etelis carbun- 

 culus (Everson 1984), and Seriola dumerili 

 (Kikkawa and Everson 1984), but none is avail- 

 able for uku and onaga. Thus, a study was under- 

 taken to determine the size at sexual maturity, 

 spawning season, and pattern of egg release of 

 uku and onaga. Size at se.xual maturity is a par- 

 ticularly important parameter used to assess and 

 evaluate the impact of fishing mortality on 

 spawning stock biomass and to determine levels 

 of optimum fishery yield (Polovina 1987). During 

 this study, we also attempted, within the con- 

 straints imposed by om* sampling progi-am, to 

 develop an efficient method for determining 

 gonad maturity. A third goal was to discern in- 

 terspecific differences between the reproductive 

 biology of the two species and to interpret those 

 differences. 



Manuscript accepted May 1989. 

 Fishery Bulletin. U.S. 87: 877-888. 



-Ralston. S. 1979. A description of the bottomfish fish- 

 eries of Hawaii, American Samoa, Guam, and the Northern 

 Marianas. A report submitted to the Western Pacific Re- 

 gional Fishery Management Council, Honolulu, 102 p. 

 Southwest Fish. Cent. Honolulu Lab.. Natl. Mar. Fish. 

 Serv., NOAA, Honolulu HI 96822-2396. 



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